All subpanels require a four wire circuit. There is one exception.
6/3 with a bare wire should have everything listed above. The bare wire will be the ground. If you only have three wires total, you are missing one wire. If this is the case you will have to pull the correct cable. This is a feeder and all the conductors are required to be in the same cable or conduit.
If this is in conduit you may be able to add the missing wire. Provided the conduit is of sufficient size.
6/3 NM always has a bare ground wire. is this NM wire?
If you have all four wires you are set. Make sure the grounds and the neutrals are separated. Do not jumper between the grds and neutrals like in the main service panel. If a factory installed jumper is present, remove it.
What size sub panel do you have? Does it have a main breaker? Please respond to these questions as they are important for a safe installation.
Last edited by J. V.; 12-06-2007 at 12:01 PM.